Electron Radiation Impact on Long Period Gratings in Different Optical Fibers

We report for the first time on the effects of electron radiation on the spectral properties of long period grating (LPG) sensors fabricated in various commercially available single-mode silica optical fibers, namely standard SMF28, a B/Ge co-doped fiber, a pure-silica core fiber, and a P-doped fiber. These LPGs were exposed to a 5.5 MeV e-beam with a dose rate of 6 kGy/min and a total accumulated dose of 192 kGy. The impact is discussed in terms of the real-time resonance wavelength shift, depending on the fiber type. To better understand the benefits and limits of utilizing this technology in specific applications, we also investigated the long-term recovery of the devices following exposure, with intermediate evaluations at 21 hours, 8 days, 6 months, and 12 months after irradiation is finished. The main findings are that LPG in B/Ge co-doped fiber is responding up to 192 kGy, with a resonance wavelength shift exceeding 35 nm and no evidence of saturation. Additionally, we demonstrated its long-term data storage potential, showing a 45% recovery toward initial values after post-irradiation stabilization. On the contrary, pure-silica core fiber maintains radiation-hardening properties against electrons. This study is the first to test the limitations of LPGs fabricated in both sensitive and radiation-hardened optical fibers, subjected to high dose rates, with a focus on both the temporary and permanent electron induced effects.